A widely-used type of electronic article surveillance (EAS) is based on RF technology, and utilises a resonance circuit operating in a dedicated part of the electromagnetic spectrum at around 8.2 MHz. If an active EAS label, hereinafter also referred to as a tag, is passed through a gate containing appropriate antennas, the resonance circuit modifies the magnetic field, and thus the presence of the EAS label can be detected.
Such technology is routinely used, for example wherein an EAS label is attached to an article for sale in a retail outlet. When the article is purchased at a Point-of-Sale (POS), the EAS label may be deactivated, which then allows the purchaser having the article to which the EAS label is still attached to pass through the gate, located near the exit to the retail outlet, without setting off an alarm. Any attempt by the purchaser to pass through the gate without the EAS label having been de-activated will result in the alarm being triggered, thereby warning the retailer of possible attempted theft of the article.
Transponders for non-contact communication with communication stations, also known as RFID, are also widely used in relation to retail articles. RFID labels are routinely attached to a wide range of retail products, and used for logistic purposes, such as item tracking and inventory control. However, compared with the main EAS frequency of 8.2 MHz, different frequency bands are allocated to RFID applications; these include 125 kHz, 13.56 MHz, 865 MHz (in Europe—the equivalent band being around 920 MHz in the United States) and 2.45 GHz.
The conventional method to deactivate an EAS label is to generate a high magnetic field which “burns” through a fuse within resonating circuit. The resonance circuit typically thus goes open circuit, and no longer is able to modify an electric field in a gate. Alternatively, and more frequently, it can make a short circuit by, for instance, burning the isolation such as dielectric between two capacitor plates. However, since the deactivation relies on a mechanical break in the resonance circuit, it may not be reliable, and the EAS label may become reactivated if the ends of the burnt fuse come into contact.
Furthermore, the de-activation is (at least intentionally) irreversible, in that once the EAS label has been deactivated, it is not possible to reactivate it, such that the EAS label is not reusable.
There is an ongoing requirement for an EAS label, which does not suffer, or suffers only to a reduced extent, from the above disadvantages.